Sheet feeding mechanism

ABSTRACT

Discrete sheets, for example container blanks, are individually withdrawn from a magazine and deposited on a conveyor by a reciprocating suction cup mechanism. A vacuum control means terminates the vacuum in the suction cups as the withdrawn sheet reaches the conveyor. A hold down mechanism is automatically actuated to contact the top surface of the withdrawn sheet as the vacuum in the suction cups is terminated, to maintain proper positioning of the withdrawn sheet on the conveyor.

United States Patent 91 Farfaglia et al.

[ 1 SHEET FEEDING MECHANISM [75] Inventors: Silvio T. Farfaglia, Fulton; Robert G. Halpin, Minetto; Ronald E. Bock, Fulton, all of NY.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

[22] Filed: Sept. 7, 1973 [21] Appl. No.: 395,027

[52] US. Cl. 271/12; 271/102; 271/108; 271/266; 271/271 [51] Int. Cl B65h 3/08; B65h 5/02 [58] Field of Search ..271/12, 5,13,102, 108, 271/266, 271

[56] References Cited UNITED STATES PATENTS 2,567,223 9/1951 Maher et a1. 271/102 2,737,389 3/1956 Evans ct al. 271/12 X June 3, 1975 2,811,352 10/1957 Bornemann .1 271/l2 X 3,137,496 6/1964 Hotchkiss et al. 271/12 FOREIGN PATENTS OR APPLICATIONS 562,278 8/1958 Canada 271/l2 Primary ExaminerEvon C. Blunk Assistant Examiner-James W. Miller [5 7] ABSTRACT Discrete sheets, for example container blanks, are individually withdrawn from a magazine and deposited on a conveyor by a reciprocating suction cup mechanism. A vacuum control means terminates the vacuum in the suction cups as the withdrawn sheet reaches the conveyor. A hold down mechanism is automatically actuated to contact the top surface of the withdrawn sheet as the vacuum in the suction cups is terminated, to maintain proper positioning of the withdrawn sheet on the conveyor.

7 Claims, 5 Drawing Figures PATENTEU 3 SHEET PATENTEUJUM3 m5 7 3,887,177

SHEET 5 FIG. .5

SHEET FEEDING MECHANISM This invention relates to apparatus for feeding discrete sheet material. In one aspect'the invention relates to means for successively feeding flat sheets from a supply magazine to a conveyor. In another aspect the invention relates to apparatus for successively withdrawing individual flat blanks from a supply magazine, depositing the withdrawn blank on a conveyor having means for engaging the blank, and maintaining the position of the withdrawn blank on the conveyor until after the blank is contacted by the blank engaging means. In a further aspect the invention relates to a mechanism for feeding sidewall blanks to a paperboard carton forming machine.

In previous sidewall blank feeding apparatus, a mechanism such as a chip feeder or a suction cup assembly has been employed to strip an individual blank from the bottom of a stack of blanks and move it to a position where the blank could be picked up by a conveyor mechanism. When employing paperboard blanks with or without a protective coating of thermoplastic material, variations in temperature and humidity in the storage location and in the processing location affect the paperboard blanks, causing the blanks to tend to curl or how. The use of a suction cup assembly to withdraw a blank from a magazine generally involves the bowing of the blank to move the blank past retaining elements. Deviations in the blank from a planar condition can cause the blank to be missed by the blank engaging mechanism of the conveyor and/or to come into interfering contact with machine elements, thus jamming the blank and interrupting the feeding of the blanks. Also, with chip feeders the feeding mechanism would occasionally slide past the supply magazine without engaging a blank, or only partially engage a blank thereby damaging the blank.

In accordance with the present invention, these disadvantages are avoided or minimized by utilizing a suction cup assembly to withdraw the blanks from the supply magazine and providing hold-down means which engages the blank after the blank is withdrawn from the supply mechanism to properly position the withdrawn blank on the conveyor and to maintain that positioning until after the blank is engaged by the conveyor.

Accordingly it is an object of the present invention to provide an improved mechanism for feeding discrete sheets. Another object of the invention is to provide accurate feeding of discrete sheets to a conveyor. Another object of the invention is to properly position sheets on a conveyor. Yet another object of the invention is to minimize damage to sheets during withdrawal thereof from a supply magazine and the subsequent transfer to a conveyor. A further object of the invention is to minimize jamming of blanks in a carton forming machine. Other objects, aspects and advantages of the invention will be apparent from a study of the specification, the drawings and the appended claims to the invention.

In the drawings,

FIG. 1 is a diagrammatic view in elevation showing the relationship of the sidewall blank feeder to the container forming machine.

FIG. 2 is a plan view of a sidewall blank feeder embodying the invention, with portions of a base sheet being broken out to show lower components.

FIG. 3 is a simplified elevation view along the line 3-3 of FIG. 2 showing the chain carrier for the sidewall blank and the cam drive for the hold-down bar.

FIG. 4 is a simplified elevation view along the line 4-4 of FIG. 2 showing the vacuum cups, the holddown bars, and the reciprocating mechanism in the down position.

FIG. 5 is a partial view in elevation along the line 5-5 of FIG. 2 showing a vacuum cup, 21 hold-down bar, and the associated reciprocating mechanism in the up position.

Referring now to FIG. 1, each of the sidewall blanks 1 is a flat, relatively stiff single sheet of paperboard, rectangular in shape, scored to provide five longitudinal panels, and coated on both the top and bottom surfaces with a thermoplastic material, e.g., polyethylene. Sidewall blanks 1 are stored in the sidewall blank magazine 2 and are removed singly from the stack by apparatus hereinafter described. The separated sidewall blank is then moved through a heater station 3 to a mandrel 5 on a turret 7 for forming a container. The mandrel 7 is intermittently rotated in a clockwise direction, as shown on the drawing, by suitable drive means, not shown. Chain 9, which is driven by turret 7, rotates shaft 11 so that shaft 11 intermittently drives sidewall conveyor chains 13.

Conveyor chains 13 have dogs 14 to engage a sidewall blank 1 after it has been withdrawn from the stack to move the sidewall blank to the heater station 3 and then to the position where the blank can be engaged by the fingers 16 and moved onto the mandrel 5 in the blank receiving station. The heater station 3 has electrically heated hot air heater 4 which heats the upper surface of one side edge of sidewall blank 1, heater 6 which heats the lower surface of the opposite side edge of sidewall blank 1, and heater 8 which heats the upper surface of the trailing end of sidewall blank 1. An air curtain is produced by downwardly directed jets of unheated air from air supply tube 10 when the operation of the machine is interrupted, thereby providing cooling for the sidewall blanks in the stack as a protection against damage of the sidewall blanks in the stack by excessive exposure to the hot air from heaters 4, 6 and 8.

Referring now also to FIGS. 2 through 5, a supply magazine cage 15 for the storage of sidewall blanks l is formed by opposing side elements 17 and 19, interconnected by opposing back and front end elements 21 and 23, having vertical guide rods 25 on their topsides. A plurality of ledges 27 extend inwardly from opposing side elements 17 and 19 and opposing end elements 21 and 23 to engage marginal portions of the bottom surface of the lowermost sidewall blank 1 to support the stack of a plurality of sidewall blanks in cage 15. The magazine cage 15 is supported above the upper run of conveyor chains 13. The blank transfer means for successively withdrawing individual blanks from the magazine cage 15 and depositing the withdrawn blanks on the upper run of conveyor chains 13 comprises vacuum cups 28 and the associated mechanism. Vacuum cups 28 are mounted between conveyor chains 13. Cups 28 are reciprocated vertically through openings 29 in plate 31 to engage the bottom surface of central portions of the lowermost sidewall blank and to remove the lowermost sidewall blank 1 from the stack of sidewall blanks in cage 15 by causing the lowermost sidewall blank to bow downwardly in the center thereof, permitting the margins of the lowermost blank to move inwardly and slip past ledges 27. Vacuum cups 28 are connected to a suitable vacuum source 30. In their lower position, cups 28 are below the upper surface of plate 31 and the upper edges of conveyor chains 13 so as not to interfere with the lateral movement of a blank by conveyor chains 13.

Each vacuum cup 28 is supported by a sleeve 35 attached to a connecting bar 32 by an arm 33 (see FIG. 1). Each connecting bar 32 is attached to the upper end of the respective shaft 37, the lower end of which has a reduced diameter and is attached to bar 39 by nut 40. Shafts 37 extend through stationary bushings 41 which are mounted in bar 38. Shafts 37 can be reciprocated vertically by means of bar 39 to raise and lower suction cups 28. Bar 39 is reciprocated vertically by the drive system comprising connecting lugs 42, links 43, arms 44 and 45, and cam wheel 46 connected to a drive motor not shown. The upper ends of arms 44 have a Y- shaped yoke to receive the respective link 43, while the lower ends of arms 44 are joined by bar 47. Each link 43 is freely rotatable about pivot pins 48 and 49 mounted in lugs 42 and arms 44, respectively. Shaft 50 extends through both arms 44 and serves as the pivot pin for the rigid lever formed by arms 44 and 45 and bar 47. The lower end of arm 45 is provided with a cam follower 51 which rides in cam track 52 in cam 46. The rotation of cam 46 about the axis of shaft 53 causes the lower end of arm 45 to rise and fall in accordance with the configuration of cam track 52, thereby causing the upper ends of arms 44 and the bar 39 to move up and down. Limit switch 54, operatively connected to a solenoid valve, not shown, is activated to release the vacuum to vacuum cups 28 when reciprocal plate 39 is in the down position by the action of adjustable stop 55, mounted on bar 39, depressing plunger 56 of the limit switch 54. Conversely, a vacuum is drawn through vacuum cups 28 to remove a sidewall blank 1 from the stack of sidewall blanks when bar 39 and vacuum cups 28 are in the up position and plunger 56 is released.

Also, attached to bar 39 are a pair of U shaped support blocks 57, each having a pivot pin 58 which extends through the sidewall of the associated sleeve 59 to allow pivotable movement of sleeve 59. The lower end of a shaft 60 is positioned within each sleeve 59 with each shaft 60 being movable vertically with respect to the associated sleeve 59. A clevis block 61 is mounted on the upper end of each shaft 60. An expansion spring 62 is mounted about shaft 60 between sleeve 59 and clevis block 61. Crank shafts 63 are rotatably mounted in sleeves 64 which are attached to the frame of the machine. Each crank shaft 63 is provided with an eccentric pin 65 which extends through the opening of the respective clevis block 61 and is rotatable therein. The pin 65 has a smaller diameter than the shaft 63, and the elongated axis of pin 65 is parallel to and spaced from the elongated axis of shaft 63. Shaft 63 extends through openings in arms 66 of yoke 67 which is secured to shaft 63 for rotation therewith. A hold-down bar 68 is attached in a horizontal position to the bottom surface of the inner end of yoke 67. In the upper position,'as shown in FIG. 5, the hold-down bars 68 are under side elements 17 and 19 and out of the way of a sidewall'blank 1 being withdrawn from the stack of sidewall blanks. In the lower position the holddown bars 68 overlie the side margins of a sidewall blank 1 which has been fully retracted, as shown in FIG. 4. The eccentric mounting of pin 65 on shaft 63 permits the arcual movement of hold-down bars 68 about the elongated axis of shaft 63 in response to the vertical motion of shaft and sleeve 59. Pivot pin 58 permits the pivotal motion of sleeve 59 and shaft 60 about pin 58 necessary to allow the arcuate motion of crank pin and clevis block 61. Since the distance moved upwardly by bar 39 is more than the distance required for arcual movement of crank pins 65, a slot 71 is provided in each of shafts 60. A retainer pin 72 extends through sleeve 59 and slot 71 of shaft 60 to allow vertical movement of sleeve 59 relative to shaft 60.

Switch 75 is an alarm switch activated by arm 76 when the number of sidewall blanks 1 present is insufficient to permit operation of the packaging machine and is connected to a control circuit, now shown, to cause the machine to be rendered inoperative when a sufficient number of sidewall blanks is not present.

The central portion of plate 31 is supported by suitable means, for example by beam 81 and bar 38. The outer portions of plate 31 are supported by frame members 82 and 83. Bar 38 can be supported by curved elements 84 and 85, secured to frame members 82 and 83, respectively. The frame members 82 and 83 can be secured to the angle iron frame members 86 and 87. Channel members 88 and 89 serve as guides for the upper flight of the conveyor chains 13. Details of the frame structure have been simplified or omitted for the sake of clarity of the drawings.

In operation, in the initial or starting position the chains 13 are stationary, reciprocal bar 39 is in its lowermost position, hold-down bars 68 are in the down position, the stack of sidewall blanks 1 is resting on ledges 27, and plunger 56 of the valve 54 is depressed breaking the vacuum.

In the down position, illustrated in FIG. 4, the spring 62 is under sufficient compression to retain the shaft 60 elevated to the extent permitted by pin 72 engaging the lower end of slot 71. As bar 39 is elevated, springs 62 maintain the shafts 60 in the elevated position with the bottom of slots 71 engaging pins 72. The upward movement of shafts 60 starts the rotative movement of the crank pins 65 to move the hold-down bars 68 from the down position to the up position. As the upward movement of bar 39 continues, the upper end of yokes 67 move against adjustable stops 73 mounted on the frame. by arm 74, thereby terminating the rotation of crank pins 65 and the upward motion of shafts 60. Further upward movement of bar 39 results in relative motion of sleeves 59 with respect to shafts 60, permitted by the movement of pins 72 upwardly in slots 71. The upward movement of bar 39 terminates before pins 72 would reach the upper ends of slots 71. At the end of the upward movement of bar 39 the suction cups 28 have contacted the bottom side of the lowermost sidewall blank -1, the plunger 56 has been released to open the suction cups 28 to the reduced pressure of the vacuum source, thereby securing the lowermost sidewall blank 1 to the suction cups. The reciprocal bar 39 then begins its downward movement, permitting vacuum cups 28 to pull the bottommost sidewall blank 1 from the stack past the ledges 27 and move it downward into position over the upper run of chains 13 and in front of a pair of lugs 14. Although sleeves 59 move downwardly with bar 39, the compression of the springs 62 retain the hold-down bars 68 in the retracted position under elements 17 and 19 with yoke 67 against stops 73 during the initial portion of the downward movement of bar 39 and sleeves 59, the pins 72 moving downwardly in the slots 71. As the reciprocal bar 39 approaches its lowermost position with the plane of the withdrawn sidewall blank 1 being below the hold-down bars 68, the pins 72 engage the lower end of slots 71, thereby causing shafts 60 to move downwardly with the sleeves 59. The downward motion of shafts 60 causes the rotation of the hold-down bars 65 downwardly against the top edges of the withdrawn sidewall blank 1. Immediately prior to bar 39 reaching its lowermost position and after the bars 68 have started their downward rotation, the plunger 56 of limit switch 54 is contacted by adjustable stop 55, thus breaking the vacuum to the cups 28. Thus, hold-down bars 68 serve to maintain the withdrawn sidewall blank 1 in place on plate 31 after the vacuum to suction cups has been terminated, thereby assuring proper engagement of the withdrawn blank by the dogs 14. However the downward force exerted by hold-down bars 68 is sufficiently small to avoid interference with the forward movement of the withdrawn sidewall blank 1 by the dogs 14 of conveyor 13. After the reciprocal bar 39 reaches its lowermost position, the chains 13 are indexed by common drive 11 and the dogs 14 push the withdrawn sidewall blank 1 laterally along the upper run of conveyor chains 13 to the heater station 3. Simultaneously, another set of dogs 14 moves the blank 1 which had been at the heater station to the position where the rear edge of the heated blank is engaged by fingers 16. The fingers 16 then move the heated blank onto the mandrel 5 in the blank receiving station of turret 7. The cycle is then repeated to move additional sidewall blanks 1 singly from cage through heater station 3 and onto the mandrel 5 in the blank receiving station of turret 7.

Reasonable variations and modifications are possible within the scope of the foregoing disclosure, the drawings and the appended claims to the invention. For example, the hold-down bars 68 can be spring mounted.

on yokes 67, and two or more hold-down bars can be employed on each side of the blank instead of the single bar illustrated. The invention can be employed with continuously actuated conveyors as well as intermittently indexed conveyors. Cams or other suitable means could be employed to maintain the bars 68 in the retracted position until after passing of the withdrawn blank, instead of the sleeves 59, shafts 60, springs 60, and pins 72. Switch 54 can be actuated to release the blank as the blank reaches plate 31 or at any point before reaching plate 31 but after bars 68 have been rotated outwardly over the withdrawn blank. While four suction cups 28 have been illustrated, a single suction cup or any other suitable number of suction cups could be employed. Although the invention has been described in terms of mechanism for processing rectangular sheets, it can be employed with sheets of other configuration, for example trapezoidal or arcuate configurations.

That which is claimed is:

1. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run;

a supply magazine means for containing a plurality of said sheets, each of said sheets in said magazine means having first and second opposite edges extending generally in the direction of movement of said conveyor run, means for mounting said supply magazine means over said conveyor run;

transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run, said transfer means comprising at least one suction cup, means mounted beneath said conveyor run adapted to move said at least one suction cup upwardly through said conveyor run into engaging contact with the bottom one of said sheets in said supply magazine means and then to return said at least one suction cup downwardly through said conveyor run to deposit the withdrawn sheet on said conveyor run, and means for maintaining a vacuum in said at least one suction cup from the time said at least one suction cup contacts the bottom sheet in said supply magazine to the time the withdrawn sheet is deposited on said conveyor run;

holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means, said first holddown means being positioned to engage the upper surface of the first edge of the sheet deposited on said conveyor run and said second hold-down means being positioned to engage the upper surface of the second edge of the sheet deposited on said conveyor run; and

means for actuating said holding means to contact said thus withdrawn individual sheet as the sheet is being deposited on said conveyor run comprising a first pair of horizontally positioned shafts, means for mounting said first hold-down means on one of said first pair of shafts for rotation therewith, means for mounting said second hold-down means on the other of said first pair of shafts for rotation therewith, a second pair of vertically positioned shafts, means for moving said second pair of shafts at least generally vertically responsive to the vertical movement of said at least one suction cup, means responsive to the generally vertical movement of one of said second pair of shafts for rotating said one of said first pair of shafts, means responsive to the generally vertical movement of the other of said second pair of shafts for rotating said other of said first pair of shafts.

2. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run;

a supply magazine means for containing a plurality of said sheets, each of said sheets in said magazine means having first and second opposite edges extending generally in the direction of movement of said conveyor run, means for mounting said supply magazine means over said conveyor run;

transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run, said transfer means comprising at least one suction cup, means mounted beneath said conveyor run adapted to move said at least one suction cup upwardly through said conveyor run into engaging contact with the bottom one of said sheets in said supply magazine means and then to return said at least one suction cup downwardly through said conveyor run to deposit the withdrawn sheet on said conveyor run, and means for maintaining a vacuum in said at least one suction cup from the time said at least one suction cup contacts the bottom sheet in said supply magazine to the time the withdrawn sheet is deposted on said conveyor run;

holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means, said first holddown means being positioned to engage the upper surface of the first edge of the sheet deposited on said conveyor run and said second hold-down means being positioned to engage the upper surface of the second edge of the sheet deposited on said conveyor run; and

means for actuating said holding means to contact said thus withdrawn individual sheet as the sheet is being deposited on said conveyor run comprising a first pair of horizontally positioned shafts, means for mounting said first hold-down means on one of said first pair of shafts for rotation therewith, means for mounting said second hold-down means on the other of said first pair of shafts for rotation therewith, a second pair of vertically positioned shafts, first and second vertically positioned sleeves, one of said second pair of shafts being positioned within and extending above said first sleeve, the other of said second pair of shafts being positioned within and extending above said second sleeve, each of said second pair of shafts having a clevis block secured to the upper end thereof and being provided with a spring positioned between and under compression by the respective clevis block and the respective sleeve, each of said second pair of shafts having a vertically extending slot therein, each of said sleeves having a pin therein extending through the slot of the associated one of said second pair of shafts to permit relative motion between each of said sleeves and the associated vertical shaft to the extent of the slot in the associated vertical shaft, means responsive to the generally vertical movement of one of said clevis blocks for rotating said one of said first pair of shafts, means responsive to the generally vertical movement of the other of said clevis blocks for rotating said other of said first pair of shafts, and means for moving said first and second sleeves at least generally vertically responsive to the vertical movement of said at least one suction cup.

3. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run;

a supply magazine means for containing a plurality of said sheets, means for mounting said supply magazine means over said conveyor run;

transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run, said transfer means comprising at least one suction cup, means mounted beneath said conveyor run adapted to move said at least one suction cup upwardly through said conveyor run into engaging contact with the bottom one of said sheets in said supply magazine means and then to return said at least one suction cup downwardly through said conveyor run to deposit the withdrawn sheet on said conveyor run, and means for maintaining a vacuum in said at least one suction cup from the time said at least one suction cup contacts the bottom sheet in said supply magazine to the time the withdrawn sheet is deposited on said conveyor run;

means for periodically activating said conveyor means, and means for reciprocating said at least one suction cup to withdraw the bottom one of said sheets in said supply magazine means; and

holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means positioned to engage the upper surfaces of opposite edges of the sheet being deposited on said conveyor run; each said hold-down means comprising a first shaft, a hold-down bar, means mounting said hold-down bar on said first shaft for rotation therewith, a second shaft, means for longitudinally moving said second shaft responsive to the vertical movement of said at least one suction cup, and means respon sive to the longitudinal movement of said second shaft for rotating said first shaft and the associated hold-down bar.

4. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run;

a supply magazine means for containing a plurality of said sheets, each of said sheets in said magazine means having first and second opposite edges extending generally in the direction of movement of said conveyor run;

transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run;

holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means, said first holddown means being positioned to engage the upper surface of the first edge of the sheet deposited on said conveyor 'run and said second hold-down means being positioned to engage the upper surface of the second edge of the sheet deposited on said conveyor run; and

means for actuating said holding means to contact said thus withdrawn individual sheet as the sheet is .being deposited on said conveyor run comprising a first pair of horizontally positioned shafts, means for mounting said first hold-down means on one of said first pair of shafts for rotation therewith, means for mounting said second hold-down means on the other of said first pair of shafts for rotation therewith, a second pair of vertically positioned shafts, first and second vertically positioned sleeves, one of said second pair of shafts being positioned within and extending above said first sleeve, the other of said second pair of shafts being positioned within and extending above said second sleeve, each of said second pair of shafts having a clevis block secured to the upper end thereof and being provided with a spring positioned between and under compression by the respective clevis block and the respective sleeve, each of said second pair of shafts having a vertically extending slot therein, each of said sleeves having a pin therein extending through the slot of the associated oneof said second pair of shafts to permit relative motion between each of said sleeves and the associated vertical shaft to the extent of the slot in the associated vertical shaft, means responsive to the generally vertical movement of one of said clevis blocks for rotating said one of said first pair of shafts, means responsive to the generally vertical movement of the other of said clevis blocks for rotating said other of said first pair of shafts, and means for moving said first and second sleeves at least generally vertically responsive to the vertical movement of said transfer means 5. Apparatus in accordance with claim 1 further comprising means for periodically activating said conveyor means, and means for actuating said transfer means during the time said conveyor means is inactive.

6. Apparatus in accordance with claim 2 further comprising means for periodically activating said conveyor means, and means for reciprocating said at least one suction cup to withdraw the bottom one of said sheets in said supply magazine means and to deposit the withdrawn sheet on said conveyor run during the time said conveyor means is inactive, said conveyor means being provided with means for engaging a deposited sheet upon activation of said conveyor means.

7. Apparatus in accordance with claim 3 wherein said means for longitudinally moving said second shaft comprises a sleeve encompassing one end of said second shaft, said second shaft having a slot therein extending longitudinally thereof, a pin passing through said slot and secured to said sleeve to permit relative movement of said sleeve and said second shaft to the extent of said slot, and spring means for preventing the longitudinal movement of said second shaft in the absence of said pin engaging an end of said slot. 

1. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run; a supply magazine means for containing a plurality of said sheets, each of said sheets in said magazine means having first and second opposite edges extending generally in the direction of movement of said conveyor run, means for mounting said supply magazine means over said conveyor run; transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run, said transfer means comprising at least one suction cup, means mounted beneath said conveyor run adapted to move said at least one suction cup upwardly through said conveyor run into engaging contact with the bottom one of said sheets in said supply magazine means and then to return said at least one suction cup downwardly through said conveyor run to deposit the withdrawn sheet on said conveyor run, and means for maintaining a vacuum in said at least one suction cup from the time said at least one suction cup contacts the bottom sheet in said supply magazine to the time the withdrawn sheet is deposited on said conveyor run; holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means, said first hold-down means being positioned to engage the upper surface of the first edge of the sheet deposited on said conveyor run and said second hold-down means being positioned to engage the upper surface of the second edge of the sheet deposited on said conveyor run; and means for actuating said holding means to contact said thus withdrawn individual sheet as the sheet is being deposited on said conveyor run comprising a first pair of horizonTally positioned shafts, means for mounting said first hold-down means on one of said first pair of shafts for rotation therewith, means for mounting said second hold-down means on the other of said first pair of shafts for rotation therewith, a second pair of vertically positioned shafts, means for moving said second pair of shafts at least generally vertically responsive to the vertical movement of said at least one suction cup, means responsive to the generally vertical movement of one of said second pair of shafts for rotating said one of said first pair of shafts, means responsive to the generally vertical movement of the other of said second pair of shafts for rotating said other of said first pair of shafts.
 2. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run; a supply magazine means for containing a plurality of said sheets, each of said sheets in said magazine means having first and second opposite edges extending generally in the direction of movement of said conveyor run, means for mounting said supply magazine means over said conveyor run; transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run, said transfer means comprising at least one suction cup, means mounted beneath said conveyor run adapted to move said at least one suction cup upwardly through said conveyor run into engaging contact with the bottom one of said sheets in said supply magazine means and then to return said at least one suction cup downwardly through said conveyor run to deposit the withdrawn sheet on said conveyor run, and means for maintaining a vacuum in said at least one suction cup from the time said at least one suction cup contacts the bottom sheet in said supply magazine to the time the withdrawn sheet is deposted on said conveyor run; holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means, said first hold-down means being positioned to engage the upper surface of the first edge of the sheet deposited on said conveyor run and said second hold-down means being positioned to engage the upper surface of the second edge of the sheet deposited on said conveyor run; and means for actuating said holding means to contact said thus withdrawn individual sheet as the sheet is being deposited on said conveyor run comprising a first pair of horizontally positioned shafts, means for mounting said first hold-down means on one of said first pair of shafts for rotation therewith, means for mounting said second hold-down means on the other of said first pair of shafts for rotation therewith, a second pair of vertically positioned shafts, first and second vertically positioned sleeves, one of said second pair of shafts being positioned within and extending above said first sleeve, the other of said second pair of shafts being positioned within and extending above said second sleeve, each of said second pair of shafts having a clevis block secured to the upper end thereof and being provided with a spring positioned between and under compression by the respective clevis block and the respective sleeve, each of said second pair of shafts having a vertically extending slot therein, each of said sleeves having a pin therein extending through the slot of the associated one of said second pair of shafts to permit relative motion between each of said sleeves and the associated vertical shaft to the extent of the slot in the associated vertical shaft, means responsive to the generally vertical movement of one of said clevis blocks for rotating said one of said first pair of shafts, means responsive to the generally vertical movement of the other of said cLevis blocks for rotating said other of said first pair of shafts, and means for moving said first and second sleeves at least generally vertically responsive to the vertical movement of said at least one suction cup.
 3. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run; a supply magazine means for containing a plurality of said sheets, means for mounting said supply magazine means over said conveyor run; transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run, said transfer means comprising at least one suction cup, means mounted beneath said conveyor run adapted to move said at least one suction cup upwardly through said conveyor run into engaging contact with the bottom one of said sheets in said supply magazine means and then to return said at least one suction cup downwardly through said conveyor run to deposit the withdrawn sheet on said conveyor run, and means for maintaining a vacuum in said at least one suction cup from the time said at least one suction cup contacts the bottom sheet in said supply magazine to the time the withdrawn sheet is deposited on said conveyor run; means for periodically activating said conveyor means, and means for reciprocating said at least one suction cup to withdraw the bottom one of said sheets in said supply magazine means; and holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means positioned to engage the upper surfaces of opposite edges of the sheet being deposited on said conveyor run; each said hold-down means comprising a first shaft, a hold-down bar, means mounting said hold-down bar on said first shaft for rotation therewith, a second shaft, means for longitudinally moving said second shaft responsive to the vertical movement of said at least one suction cup, and means responsive to the longitudinal movement of said second shaft for rotating said first shaft and the associated hold-down bar.
 3. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run; a supply magazine means for containing a plurality of said sheets, means for mounting said supply magazine means over said conveyor run; transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run, said transfer means comprising at least one suction cup, means mounted beneath said conveyor run adapted to move said at least one suction cup upwardly through said conveyor run into engaging contact with the bottom one of said sheets in said supply magazine means and then to return said at least one suction cup downwardly through said conveyor run to deposit the withdrawn sheet on said conveyor run, and means for maintaining a vacuum in said at least one suction cup from the time said at least one suction cup contacts the bottom sheet in said supply magazine to the time the withdrawn sheet is deposited on said conveyor run; means for periodically activating said conveyor means, and means for reciprocating said at least one suction cup to withdraw the bottom one of said sheets in said supply magazine means; and holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means positioned to engage the upper surfaces of opposite edges of the sheet being deposited on said conveyor run; each said hold-down means comprising a first shaft, a hold-down bar, means mounting said hold-down bar on said first shaft for rotation therewith, a second shaft, means for longitudinally moving said second shaft responsive to the vertical movement of said at least one suction cup, and means responsive to the longitudinal movement of said second shaft for rotating said first shaft and the associated hold-down bar.
 4. Apparatus for feeding discrete sheets which comprises a conveyor means having a conveyor run on which said sheets are to be transported and having means for engaging sheets deposited on said conveyor run; a supply magazine means for containing a plurality of said sheets, each of said sheets in said magazine means having first and second opposite edges extending generally in the direction of movement of said conveyor run; transfer means for successively withdrawing individual sheets from said supply magazine means and for depositing each thus withdrawn individual sheet on said conveyor run; holding means for maintaining the position of the thus deposited sheet on said conveyor run until after said thus deposited sheet is contacted by said means for engaging, said holding means comprising first and second hold-down means, said first hold-down means being positioned to engage the upper surface of the first edge of the sheet deposited on said conveyor run and said second hold-down means being positioned to engage the upper surface of the second edge of the sheet deposited on said conveyor run; and means for actuating said holding means to contact said thus withdrawn individual sheet as the sheet is being deposited on said conveyor run comprising a first pair of horizontally positioned shafts, means for mounting said first hold-down means on one of said first pair of shafts for rotation therewith, means for mounting said second hold-down means on the other of said first pair of shafts for rotation therewith, a second pair of vertically positioned shafts, first and second vertically positioned sleeves, one of said second pair of shafts being positioned within and exTending above said first sleeve, the other of said second pair of shafts being positioned within and extending above said second sleeve, each of said second pair of shafts having a clevis block secured to the upper end thereof and being provided with a spring positioned between and under compression by the respective clevis block and the respective sleeve, each of said second pair of shafts having a vertically extending slot therein, each of said sleeves having a pin therein extending through the slot of the associated one of said second pair of shafts to permit relative motion between each of said sleeves and the associated vertical shaft to the extent of the slot in the associated vertical shaft, means responsive to the generally vertical movement of one of said clevis blocks for rotating said one of said first pair of shafts, means responsive to the generally vertical movement of the other of said clevis blocks for rotating said other of said first pair of shafts, and means for moving said first and second sleeves at least generally vertically responsive to the vertical movement of said transfer means
 5. Apparatus in accordance with claim 1 further comprising means for periodically activating said conveyor means, and means for actuating said transfer means during the time said conveyor means is inactive.
 6. Apparatus in accordance with claim 2 further comprising means for periodically activating said conveyor means, and means for reciprocating said at least one suction cup to withdraw the bottom one of said sheets in said supply magazine means and to deposit the withdrawn sheet on said conveyor run during the time said conveyor means is inactive, said conveyor means being provided with means for engaging a deposited sheet upon activation of said conveyor means. 